sandythevandy avatar image
sandythevandy asked

BMS 12/200 not allowing charge to batteries from alternator

I have a 2021 Mercedes Sprinter van that I installed a victron system in, complete with 2 Victron batteries, multi plus inverter, lynx distributor and the BMS 12/200. I cannot get the alternator to charge the system. I know power is coming from the alternator, I have checked the wire. I attached all the included wires, but was also confused at what a “remote on/off” was. The alternator comes into the BMS, the middle Li-Ion Minus goes to negative on the battery and the system exits into the positive bus bar of the Lynx distributor. I have the remote on/off (I think) wires hooked into the ”remote” and they go to the positive lug of the battery. Any suggestions or changes I could try?

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nathantate avatar image nathantate commented ·

I’m having a similar issue. Victron Connect stats of BMS says alternator charging is enabled, but the green light on the physical BMS indicating alternator charging enabled is not lit up. Alternator voltage is above 13V so it should be charging.


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Matthias Lange - DE avatar image Matthias Lange - DE ♦ nathantate commented ·
The starter/alternator voltage needs to be higher for a actual current flow.
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nathantate avatar image nathantate Matthias Lange - DE ♦ commented ·
Thank you for the response @Mathias Lange! Do you know what voltage is required and any suggestions that could get my stock alternators to output the required voltage? Thanks!
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pwfarnell avatar image pwfarnell nathantate commented ·
You typically need 14.4V to charge lithium batteries. I do not know about modifying the alternator as the voltage is determined by the Engine Control Unit not the alternator on modern vehicles, see my answer below. What you can use is a DC to DC charger that will boost the alternator voltage to charge the lithium batteries. However, I do not know if that is compatible with using the BMS 12/200 or not, I think you need to do more research, I do jot know the answer. Try some van conversion sites.
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1 Answer
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pwfarnell answered ·

You have to be careful with modern vehicles with Euro V / Vi engines as the engine management system can reduce the alternator output voltage to a float level for lead acid batteries (13.4V) which will not be high enough to charge lithium batteries.

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